Well, if you have the eqipment, it is a big deal because it just looks so much better-even the crappy 480p Fox broadcasts. Once I saw the Super Bowl and NHL play-offs in HD, I can't stand non-hd broadcasts.
For those that are new to HD there are 3 resolutions supported (although only 2 are really Hi-Def). Your standard TV broadcast sends out alternating fields of 240 lines each which is interlaced-thus giving you the standard broadcast resolution refered to as 480i.
480p sends out both fields in what is called progressive scanning (simply combining both fields rather than alternating them). Basically DVD quality.
720p is the same but sends out 720 lines of resolution.
1080i is the highest HD resolution currently available (although 1080p is creeping around the corner) and is similar to 480i, with a much higher resolution. Looks almost 3-d with it's clarity.
A practical example is that in most sports broadcasts the crowd tends to be an indeterminate mass of color. In the a 1080i broadcast you can pick out idividuals from the crowd by what they are wearing. Pretty amazing stuff!
